Repairing brick mortar can be a DIY home project but consider these tips before getting started

A reader recently emailed me, seeking advice on whether to take on a do-it-yourself repair of the mortar around her brick masonry. She regularly performs hands-on maintenance around her home, she said, including mixing mortar for other brick projects, and she was especially curious about working on her house's brick support piers.

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What's so tough about slathering old bricks with mush and stacking them in place, she wondered?

After some research and a call to second-generation brick mason Teddy Pierre, I came up with a few key things to consider before addressing failing brick mortar on your own.

Mortar decay can occur for two reasons: if the mortar was improperly selected for the brick piers during a previous repair or if the original mortar deteriorated over time. The original mortar on older, historic homes typically was designed to move with the changes in moisture and temperature, but its flexibility may have become compromised over the years.

The first task is to determine whether your brick is structural or brick veneer. Brick piers, for example, are tied into your home's foundation system; they often are structural. A chimney, however, could be structural or not, depending if it is bearing a load transferred from walls.

Take a close look at areas where mortar is deteriorating. If the mortar in structural brick masonry is eroded beyond 3 inches of depth, it's too risky to take on the repair work yourself. Contact a brick mason, a structural engineer -- or both -- to get advice on the next steps.

If you've decided that the risks are minimal, next consider your comfort level when mixing up dry batches of mortar ingredients and managing messy wet mortar.

Nearly impossible to purchase pre-mixed, you should prepare to buy five-pound bags of each ingredient from a store like Masonry Products in Mid-City, then blend the dry mixes on site before adding fresh water.

Customizing mortar mixes achieves an essential goal: allowing bricks to breathe by applying mortar compatible with the composition of the clay bricks.

Brick, a staple of building construction for centuries, is generally produced in the area where it is used. St. Joe bricks, for example, are still manufactured today at St. Joe Brick Works in Pearl River.

The mortar composition for century-old brick will be different from that used for 20th century brick, which was crafted from different clay and fired harder.

Proper brick repointing --removing old mortar and replacing it -- will extend the role brick plays in the longevity of the house.

In brick tuck pointing, the old mortar is not removed, and tuck pointing can be performed for aesthetic reasons rather than for building maintenance.

According to the National Park Service's repair methods for historic building preservation, old mortar should be removed to a minimum depth of two times the width of the joint, or around 1 inch, when repointing.

The new mortar isn't likely to adhere to the old, since mortar binds with brick. An explanation of mortar styles, as well as an impressively comprehensive guide to masonry in New Orleans, is featured on the city's website.

Mortar is applied wet and weak; as it dries it strengthens while retaining permeability. Vital to the success of a repointing project is achieving the correct balance between moisture in brick and moisture in mortar.

Thirsty bricks may drink water right out of newly applied mortar, causing it to cure improperly. To avoid that, wet the bricks in advance of applying new mortar even as far ahead as overnight.

Freshly repointed bricks exposed to direct sunlight for six to eight hours also must be repeatedly misted while mortar cures.

Dozens of helpful online tutorials can teach you the proper technique for applying wet mortar. The tutorials -- I particularly like one from This Old House -- name various mortar removing tools, such as mortar saws, electric grinders with diamond-tipped blades, joint rakers, wire brushes and chisels.

Most of the instructional videos suggest that the novice will need plenty of time to make multiple passes with different kinds of trowels before a rhythm is achieved for stuffing gaps with mortar.

Don't forget to consider termites when working on piers. If your work disrupts termite bait traps drilled into your piers, contact your termite company. And, you may want to add termite shields to the top of each pier while you are already outside performing pier maintenance work.

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Maryann Miller is assistant director of the Preservation Resource Center's Operation Comeback program. She can be reached at mmiller@prcno.org.